Self-injurious behavior (SIB) occurs in approximately 10% of captive, individually housed rhesus monkeys. Neither a satisfactory explanation nor an effective therapy for this disturbing phenomenon have yet been developed. The purpose of this study was to construct preliminary behavioral and physiological profiles of monkeys diagnosed with SIB in order to provide the framework for future therapeutic studies. The subjects were 24 individually housed rhesus monkeys, 13 of which had received veterinary treatment for self-inflicted bite wounds in the past. The remaining 11 subjects were categorized as controls. Behavioral profiles were developed by observing all monkeys in 5-minute sessions using a modified frequency data collection procedure with 32 categories. Monkeys were observed on average for 60 sessions (range 40-80) spread across 12 months. Physiological profiles consisted of assays of cortisol and ACTH from blood and determination of monoamine activity (dopamine, serotonin, and norepinephrine) by assaying CSF for the metabolites of these transmitters (i.e., HVA, 5-HIAA, and MHPG). For these determinations, the monkeys were anesthetized with telazol followed by rapid collection of 10 ml of blood and 1.5 ml of CSF. Behavioral profiles were found to vary across groups in that monkeys with SIB displayed higher levels of threat and vocalization and lower levels of submissive behavior than controls. SIB was distinct from other forms of stereotypic behavior because subjects with high levels of SIB did not typically show high levels of stereotypy. Although self-biting was the necessary precursor to self-injury (all the SIB monkeys engaged in biting episodes), its presence did not reliably identify monkeys with a propensity for self injury inasmuch as 8 control subjects also showed self-biting behavior. Physiological profiles did not vary as a function of SIB status. SIB and control subjects did not differ in either their levels of stress (ACTH and cortisol) or their levels of basal monoamine activity (HVA, 5-HIAA, or MHPG). Future physiological studies will involve assessing the effects of perturbations of these systems (e.g., stress challenges) on self-injurious behavior.